First, I would personally do it without a doubt, changing transmission fluid when it's needed to be done seems like a no brainer to me.
Also, I would suggest you to strictly get transmission fluid from your Toyota/Lexus dealer. They have the fluid with the right specification for you transmission.
I've done tranny fluid change 2 times yet on my car, both time with Toyota fluid ; once at a local shop and once at my Lexus dealer.
Both did a very good job and both price were very similar since Lexus dealer sold me fluid at bulk price.
I'll go at Lexus anytime again for this type of repair/service
At the end, feel free to make our own mind, but I wouldn't be stressed about laying some money for such an important maintenance service.
You'll be the one rewarded in the long run!
Good luck
Simon